Self-powered broadband photodetector based on pyramid-structured Si/TiO₂ heterojunction

Abstract Traditional Si-based photoconductive detectors face problems such as low response in the ultraviolet (UV) and infrared regions, high dark current, and low light absorption efficiency, which seriously limit their applications in the field of high-performance wide-spectrum detection. In this study, a self-powered broadband photodetector based on a Si/TiO 2 heterojunction is proposed. The detector has a pyramidal structure. By constructing a pyramidal microstructure on the surface of silicon, the light capture and absorption efficiency is significantly improved, representing a breakthrough in response performance in the visible and near-infrared (NIR) bands. In order to further enhance the photoelectric response in the UV band, a TiO 2 layer was coated on the surface of the silicon pyramid through a simple spin-coating method and annealing process. The introduction of TiO 2 effectively broadened the spectral response range of the photoelectric detector and further improved the light absorption of the device. Meanwhile, due to the built-in electric field formed by the n-TiO 2 /p-Si heterojunction, the dark current was effectively reduced, and the responsivity was improved. Experiments showed that the device exhibits high responsivity, high detectivity, and relatively low dark current in the range of 365–1305 nm. Under light at 780 nm, the device’s on–off ratio reached 2.7 × 10 3 ; its specific detectivity, D * , was 3.9 × 10 11 Jones; and its responsivity reached 0.174 A/W. In addition, this detector does not require the assistance of expensive equipment. Its preparation process is simple and inexpensive, and there is no need for an external power supply, which gives it broad application potential in wearable devices, environmental monitoring, communications, biosensing, and other fields. This study provides a brand-new strategy for the design of new wide-spectrum detectors.